Abstract
Low cycle fatigue tests were performed under repeated two-step variable sham amplitude on a low alloy steel, SFVQ1A, which is used for pressure vessels of nuclear power plants. Fatigue cracks initiated at inclusions located at the specimen surface. However, internal cracks could be found on the fracture surface of the specimens. In order to prevent fatigue crack initiation and growth on the specimen surface, polishing treatments were conducted repeatedly after applying fatigue damage of a half of the fatigue life. This procedure removed small surface cracks initiated on the surface and the fracture origin became internal. Beach marks were formed on the fracture surfaces by the repeated two-step variable strain amplitude loading. Fracture mechanics approach was applied to evaluate the growth characteristics of the surface and internal fatigue cracks.
